On the expression of polydactylism in the wings of fowl

Abstract

TWO FIQURESPolydactylism is a well-known and ancient mutation of fowl. In its most typical manifestation it accounts for the presence of five instead of four toes on each foot and as such is a standard trait of several breeds of chickens.Polydactylism of fowl is produced by duplication of the anlage material for the first digit. The type and degree of this duplication are very variable and the many resulting forms of expression haVe been the subject of repeated morphological description. All observations on the genetic behavior of polydactylism in chickens have been based on the structure of the toes.It was shown, however, by Barfurth ( '10, ' 11, '14) that the wings are also involved in the expression of polydactylism. He found in embryos of polydactylous breeds (Houdan, Orpington, Silky) that on the eighth day of development a small bud-like structure appeared on the radial margiii of the hand. This protrusion increased in size during the ninth and tenth day, at the same time acquiring a somewhat more finger-like independence. The formation of pre-cartilage and of small amounts of cartilage were observed, but this did in no case progress to the appearance of phalanges. On the tenth or eleventh day the finger-bud became constricted at its base and this constriction continued until finally the primordium was lost. A similar account of the formation and subsequent loss of such a transitory finger primordium was given by Schmalhausen ('34) for embryos of Faverolle fowl.We had occasion to make extensive observations on wings of embryos and chicks from polydactylous stock of Houdan-crossbred and Dorking origin. The following results seemed worthy of record. APPEARANCE AND PERSISTENCE OF SUPERNUMERARY DIGITSIt was possible in our material to distinguish as early as the beginning of the eighth day of development between the presence and ab-225

Evolutionary Mechanisms of Limb Loss in Tetrapods

“…The extra toe in these races is not an atavistic expression of the missing digit V, but duplicates part of the first digit (Gruneberg, 1963, p. 211). In some stocks Po causes duplication of digits in the wings at a frequency which can be altered by selection, indicating the presence of modifiers (Baumann and Landauer, 1944).…”

Evolutionary Mechanisms of Limb Loss in Tetrapods

“…Punnet and Pease (1930) concluded after extensive breeding experiments that the expression of an extra toe in some races of chickens, originally thought to be inherited as a single dominant gene Po, is under polygenic control. In some stocks Po causes duplication of digits in the wings at a frequency which can be altered by selection, indicating the presence of modifiers (Baumann and Landauer, 1944). The extra toe in these races is not an atavistic expression of the missing digit V, but duplicates part of the first digit (Gruneberg, 1963, p. 211).…”

The renal fascia

“…If the fluid is injected rapidly the stage just described may be missed, or the two layers may be disrupted, giving rise to the erroneous impression that the renal fascia is like an open inverted sac. Zuckerkandl (1883), Sappey (1889), Gerota (1895), Gosset (1907), Southam (1923), Baumann (1945), and many others state that the two layers are not fused beneath the kidney, or form a funnel under it. Martin (1942) mentions that they are weakly fused inferiorly, and I believe this is correct and that the weakest spot is at the inferomedial angle of the perinephric space adjacent to the ureter.…”